FCC Announcement: new 5GHz spectrum for Wi-Fi

First, this was just a pre-announcement, in an interview at the CES show. We won’t know the full specifics until an FCC open meeting on 20 February 2013, when the Notice of Proposed Rule Making will be published. So the notes below are brief, and subject to revision as we get better information. Further, the NPRM is the beginning of an FCC process where comments will be received and considered. Current users of the affected spectrum will want to make sure their interests are respected, and will be filing comments with the FCC. We think it may take the balance of 2013 before the new rules are cut and dried.

The thrust of the announcement is that the FCC continues to look for ways to make more spectrum available for wireless communications, including unlicensed spectrum. To that end, the NPRM will propose adding two new segments of spectrum to that available for Wi-Fi, and modifying a third segment, all in the 5GHz band used by 802.11a, 802.11n and the forthcoming 802.11ac protocols.

The two new bands are 5350-5470MHz and 5850-5925MHz, for a total of 195MHz. We estimate this could allow up to 12 new 20MHz channels in the 5GHz band (depending on how we count, there are ~25 channels available today).

Since there are incumbent users of these new channels, including government users, we expect the new spectrum will be subject to sharing protocols. It will be interesting to see what the NPRM proposes in this regard; there are some precedents for spectrum sharing and considerable work has been done already in various IEEE 802.11 groups to develop such protocols.

Dynamic Frequency Selection is already a requirement for some 5GHz channels. This is a protocol that automatically moves access points and clients away from a channel when certain transmissions are detected. We expect some of the new channels, probably all in the 5350-5470MHz range, to be subject to DFS.

The third segment of spectrum is 5600-5650MHz. This was already allocated for Wi-Fi, but it is used by Terminal Doppler Weather Radars, and following some incidents where early Wi-Fi equipment was found to be causing interference to weather radars, the FCC imposed a moratorium on new certifications a couple of years ago. Weather radars, usually around airports, play an important role in public safety, so the FCC just closed the band temporarily to avoid any new problems. The new NPRM is expected to include rules that will allow compliant Wi-Fi equipment to operate in this band again.

This is good for Wi-Fi: up to 50% increase (depending how the bands are defined: reports in the press cite a 35% increase so we may be a little optimistic here) in channels in the 5GHz band that is increasingly important, as many consumer Wi-Fi devices are now becoming dual-band. The forthcoming 802.11ac protocol supports wider channels, 80 and 160MHz, and the new rules should allow more of these wide channels to be used in the 5GHz band, giving Gigabit+ throughput.

We need to see what protocols will be required for spectrum sharing, but it is likely that existing equipment will not be field-upgradeable to support the new channels. And it will be a while before the rules are finalized, equipment is re-designed, re-certified and available on the market, perhaps into 2014. But this is a very encouraging announcement for Wi-Fi.